Conventionally, an operation apparatus including a rotation operation knob that is rotated is provided in an instrument panel and the like of an automobile. When the rotation operation knob is rotated, an operation target such as temperature or an amount of air flow of an air conditioner is operated.
For example, Related Art 1 discloses an operation apparatus 501, as shown in FIG. 8. The operation apparatus 501 includes a circuit board 520, an operation knob 540, a holder 550, and a holding member 560 (a base in Related Art 1). A switch element is mounted on the circuit board 520. The operation knob 540 operates the switch element by being rotated. The holder 550 is connected to the operation knob 540 so as to be integrally rotatable with the operation knob 540. The holding member 560 is latched to the circuit board 520 and also holds the holder 550 and the operation knob 540 so as to be capable of rotation. A plurality of through-holes 522 are formed on the circuit board 520, running through both surfaces thereof. The holding member 560 has a plurality of latched portions 567. The latched portions 567 are inserted through the through-holes 522 and extend in a front-back direction of the circuit board 520. A latched projection 567b is provided to an end of the latched portion 567 on a reverse side. The latched projection 567b projects outward in a rotation diameter direction of the operation knob 540. In a state where the latched portion 567 is inserted through the through-hole 522, the latched projection 567b contacts the surface on the reverse side of the circuit board 520 from the reverse side. The holding member 560 is latched to the circuit board 520 via this contact.
In the conventional operation apparatus 501, the latched portion 567 is inserted through the through-hole 522 on the circuit board 520 and the latched projection 567b on the latched portion 567 contacts the surface on the reverse side of the circuit board 520. Then, the holding member 560 is latched to the circuit board 520 via this contact. Therefore, setting dimensions for the latched projection 567b and the through-hole 522 is difficult. For example, in a case where a hole diameter of the through-hole 522 is made smaller and the latched projection 567b is set so as to be forcibly pushed into the through-hole 522, the work of inserting the latched projection 567b through the through-hole 522 becomes challenging. In other words, the work of attaching the holding member 560 to the circuit board 520 becomes challenging. Meanwhile, in a case where the hole diameter of the through-hole 522 is made larger, the work of attaching the holding member 560 to the circuit board 520 becomes easier. However, in such a case, the latched projection 567b becomes able to easily pass through the through-hole 522. Therefore, in such a case, after the holding member 560 is attached to the circuit board 520, there is a risk that the latched projection 567b may pass through the through-hole 522. In other words, there is a risk that the latched projection 567b will escape to an obverse side of the circuit board 520 and the holding member 560 will separate from the circuit board 520.